1. Technical Field
A method of manufacturing a silicon on insulator (hereinafter referred to as SOI) substrate is disclosed in this specification.
2. Description of Related Art
In Japanese Patent Application Publication No. 2007-173422 (JP 2007-173422 A), a semiconductor device using an SOI substrate is disclosed. The SOI substrate has a structure in which an insulating layer is in contact with a surface of a rear side semiconductor layer and a device layer is in contact with a surface of the insulating layer. In this specification, a semiconductor layer on a side on which a semiconductor element structure that is operated as a diode, a switching element, or the like is fabricated is called a device layer. The insulating layer not only covers the surface of the rear side semiconductor layer but also covers a side surface and a rear surface of the rear side semiconductor layer in some cases. When the insulating layer covers the entire surface of the rear side semiconductor layer, the insulating layer is called a box layer.
In the semiconductor device in JP 2007-173422 A, in a region in the vicinity of a rear surface of the device layer (in the vicinity of an interface between the device layer and the box layer), a high concentration region having a higher impurity concentration than a surface side is provided. When the high concentration region is provided in the vicinity of the rear surface of the device layer, a withstand pressure of the semiconductor device in a vertical direction (that is, a withstand pressure in a direction from the device layer to the rear side semiconductor layer) is improved.